The application relates generally to heat exchangers.
Conventional chilled liquid systems used in heating, ventilation and air conditioning systems include an evaporator to effect or implement a transfer of thermal energy between the refrigerant of the system and another fluid, generally a liquid to be cooled. One type of evaporator includes a shell with a plurality of tubes forming a tube bundle(s) inside the shell. The fluid to be cooled is circulated inside the tubes and the refrigerant is brought into contact with the outer or exterior surfaces of the tubes, resulting in a transfer of thermal energy between the fluid to be cooled and the refrigerant. The heat transferred to the refrigerant from the fluid to be cooled causes the refrigerant to undergo a phase change to a vapor, that is, the refrigerant is boiled on the outside of the tubes. For example, refrigerant can be deposited onto the exterior surfaces of the tubes by spraying or other similar techniques in what is commonly referred to as a “falling film” evaporator. In a further example, the exterior surfaces of the tubes can be fully or partially immersed in liquid refrigerant in what is commonly referred to as a “flooded” evaporator. In yet another example, a portion of the tubes can have refrigerant deposited on the exterior surfaces and another portion of the tube bundle can be immersed in liquid refrigerant in what is commonly referred to as a “hybrid falling film” evaporator.
As a result of the transfer of thermal energy from the fluid being cooled, the refrigerant is heated and converted to a vapor state, which is then returned to a compressor where the vapor is compressed, to begin another refrigerant cycle. The cooled fluid can be circulated to a plurality of heat exchangers located throughout a building. Warmer air from the building is passed over the heat exchangers where the cooled fluid is warmed while cooling the air for the building. The fluid warmed by the building air is returned to the evaporator to repeat the process.